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义务教育课程标准实验教材(华东师大版)九年级上册的某种同步练习册中有一道练习题颇令师生踌躇,原题是:计算:(1+mn)÷(1-mn)(m2-n2).一部分人认为该题括号间的各部分都是二级计算,应先除后乘按先后顺序计算,即:(1+mn)÷(1-mn)(m2-n2)=(mm+n÷mm-n)(m2-n2)=mm+-nn[(m+n)(m-n)]=
Compulsory education curriculum standard experiment textbooks (East China Normal University Edition) A certain kind of synchronous exercise book in the grade nine books is a teacher and student, and the original title is: Calculation: (1+mn)÷(1-mn) ( M2-n2). Some people think that the parts between the brackets are secondary calculations, which should be divided by the order of precedence: (1+mn)÷(1-mn)(m2-n2)= (mm+n÷mm-n)(m2-n2)=mm+-nn[(m+n)(mn)]=